[NFC][LoopVectorize] Move WideningDecision close to its first use.

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

if (isa<LoadInst>(I))
       // Loading the same address always produces the same result - at least
       // assuming aliasing and ordering which have already been checked.
       return true;
     // Storing the same value on every iteration.
     return TheLoop->isLoopInvariant(cast<StoreInst>(I)->getValueOperand());
   };
 
   auto isUniformDecision = [&](Instruction *I, ElementCount VF) {
+    if (isUniformMemOpUse(I))
+      return true;
+
     InstWidening WideningDecision = getWideningDecision(I, VF);
     assert(WideningDecision != CM_Unknown &&
            "Widening decision should be ready at this moment");
 
-    if (isUniformMemOpUse(I))
-      return true;
-
     return (WideningDecision == CM_Widen ||
             WideningDecision == CM_Widen_Reverse ||
             WideningDecision == CM_Interleave);
   };
 
-
   // Returns true if Ptr is the pointer operand of a memory access instruction
   // I, and I is known to not require scalarization.
   auto isVectorizedMemAccessUse = [&](Instruction *I, Value *Ptr) -> bool {
     return getLoadStorePointerOperand(I) == Ptr && isUniformDecision(I, VF);
   };
 
   // Holds a list of values which are known to have at least one uniform use.
   // Note that there may be other uses which aren't uniform.  A "uniform use"